Lumbar Facetectomy

The synovial joints between the superior and inferior articular processes on adjacent vertebral bodies are termed the facet joints. The facet joint (also known as zygapophysial joint or Z-joint) is an important load-bearing structure in the spine.[1]  A gradually increasing shear load in the lower spine explains why the surface areas of the lumbar facet joints increase from L-1 to S-1. Also, the facet joint angle in the coronal plane increases, from a mean of 25º at L1–2 to about 53º at L5–S1.[2, 3, 4]

This joint plays a role in preventing extension, rotation, and anterior displacement[5]  while permitting gliding movements between the verterbrae. Lumbar facet joints remain in constant motion, providing the spine with the stability and flexibility supporting everyday activities. For more information about the relevant anatomy, see Lumbar Spine Anatomy. 

Images depicting facetectomy can be seen below.

A remodeling process in the facets has been seen to occur in cases of damage to the joint's bone structure and ligamentous capsule. Although this process can stabilize the joint, it may also lead to nerve root impingement and radiculopathy.[2] Degeneration of the facet’s articular cartilaginous surface may cause hypertrophy of the articular surface, which can in turn lead to stenosis. It may also result in changes in the alignment and loss of mobility. As such, in addition to disc disorders, facet joint instability, degeneration, and injuries have been associated with low back pain, radiculopathy, and other spinal disorders.[1]  Additionally, osteoarthritis of the facet joint can result in synovial cyst formation and subsequent back pain unrelated to a disc degeneration.

A lumbar facetectomy is a surgical procedure to remove the prssure of the spinal nerve roots near the facet joint when conservative medical treatment fails to control pain and other symptoms of facet disease.

Indications

Lumbar facetectomy may be performed in a partial (typically medial) or a complete way. It may also be performed unilaterally or bilaterally, depending upon the pathology and mechanism(s) of injury.[6]

Pathologies requiring a facetectomy procedure include the following:

• Degenerative spine disease, which is by far the most common indication

• Traumatic injury to the spine such as a fracture and/or subluxation requiring open reduction and fixation

• Congenital conditions such as kyphoscoliosis or other states of malalignment

• Neoplasms of the spine, in particular ones involving nerve roots such as schwannoma or neurofibroma

• Vascular lesions of the spine extending along a nerve root sleeve such as a spinal arteriovenous malformation

• Inflammatory conditions or infections of the spine leading to spinal destruction, misalignment, and requiring surgical reduction and fixation

Medial facetectomy

Medial facetectomy (the most commonly performed form of facetectomy) is usually performed in conjunction with a lumbar laminotomy or laminectomy and foraminotomy and is carried on with or without discectomy. In the setting of degenerative spine disease, this operation is indicated in cases refractory to medical and conservative treatment, such as anti-inflammatory treatment, physical therapy, pain management, and so on.[7] Indications for this procedure include the following:[8, 9]

• Facet hypertrophy resulting in foraminal stenosis on imaging studies (MRI or CT myelogram), and painful radiculopathy

• Facet hypertrophy resulting in symptomatic central stenosis, in the setting of advanced degenerative changes

• Foraminal stenosis caused by other osteophytic changes, degenerative disc disease, or herniated nucleus pulposus

• Neurogenic Claudication

• Presence of a symptomatic synovial cyst

It is important to inform the patient that the main goal of this procedure is to relieve compression at the level of the foramen to treat a leg pain and radiculopathy. This procedure is not designed or indicated to treat primary axial back pain.[8]

Complete facetectomy

This procedure is usually performed in the setting of a lumbar fusion, such as transforaminal or posterior lumbar interbody fusion and pedicle screw fixation. Alternatively, it may be performed unilaterally in the setting of a far lateral disc herniation (foraminal disc herniation). Removing one facet joint in its entirety does carry a more elevated risk of instability when combined with a decompressive procedure such as laminectomy (especially in extension, where alterations in rotational motion, flexibilities, and coupled motion are seen) and, while it may be performed as a standalone procedure,[10] it is usually best when combined with instrumentation and fusion.[1, 11]

When unilateral facetectomy is carried out alone, without disruption of other posterior elements (ie, preservation of the spinous processes, interspinous and supraspinous ligaments, laminas, as well as the contralateral facet joint), the risk of instability is much lower (less than 3%).[12]

Alternatives to medial facetectomy have been suggested, such as partial medial and lateral facetectomies with preservation of at least 50% of the facet joint, in cases of foraminal pathologies. This has been demonstrated to carry a lower risk of instability,[13, 14] however, this view has been recently questioned.[10, 15]

Contraindications

Contraindications for medial facetectomy (performed in conjunction with a lumbar laminotomy or laminectomy and foraminotomy) include the following:[9]

• An absence of neural compromise on imaging studies

• Instability or deformity on imaging studies precluding further decompression without consideration for fusion

• Skin or soft tissue infection at the site of the projected incision

• Medical comorbidities or advanced age precluding the patient from undergoing surgical intervention

Anesthesia

General anesthesia with endotracheal (ET) intubation is typically used. A reinforced tube should be used because the patient is in the prone position and tube kinking is a risk to airway compromise. The ET tube should be adequately secured to the mouth with strong tape to prevent dislodgement when positioning.

In cases in which intraoperative monitoring is used, such as SSEP, EMG, or MEP, the anesthesiologist should be made aware prior to the onset of induction so as to use medications that will not affect the electrophysiological readings (eg, avoiding muscle relaxants).

Alternatively, if the patient is unable or unwilling to undergo general anesthesia, the procedure may be performed under conscious sedation and local or spinal anesthesia.[9]

Equipment

Standard surgical equipment for lumbar spine surgery is used. This includes the following:

• Self-retaining or tubular retractor

• Curettes

• Kerrison punch

• Leksell rongeurs

• Pituitary rongeurs

• High-speed drill with matchstick type bit

• Nerve root retractor

• Loop or microscope magnification

• Headlight illumination

If a complete facetectomy is to be performed, then the use of osteotomes and a mallet should be considered to remove the facet in an en bloc fashion. 

Operative adjuncts also include the following:

• C-arm fluoroscopy

• Radiolucent table

• Wilson frame

• Neuromonitoring

Preoperative studies are crucial in planning the surgical approach and determining indications. These include the following:[16]

• MRI: exiting nerve roots are visualized on the axial T2-weighted images and parasagittal T2-weighted images as well. Facet hypertrophy or synovial cyst may be evident. Gadolinium contrast can be administered in cases of reoperation to outline epidural fibrosis versus recurrent disc herniation or synovial cyst.

• 3D reconstruction thin cut CT scan: used to outline bony elements, look for possible spontaneous fusion, osteophytes, calcified ligaments, pars integrity, etc. The addition of myelography contrast enables visualization of neural elements and assessment of the degree of stenosis. This is especially helpful in patients unable to undergo MRI studies.

• Plain x-rays with flexion/extension views (dynamic studies): enables determination of instability by subluxation and pars integrity.

Positioning

The patient is positioned prone on a Wilson frame with the hips and knees flexed if a decompression procedure is to be performed to straighten the lumbar lordosis and to open the interlaminar space.

In cases where fusion is contemplated, the back should be in the neutral position, as such, the Jackson radiolucent table is used and the patient is rotated in the prone position while maintaining neutral alignment of the lumbar spine.

In both cases, the patient’s abdomen is allowed to hang freely in order to avoid increased intra-abdominal pressure and reduce bleeding intraoperatively.

Complication prevention

Preoperative antibiotics are used for infection prophylaxis and are continued for 24 hours, unless a drain is used, in which case they are continued until the drain is removed.

Deep venous thrombosis prophylaxis should be initiated intraoperatively in the form on sequential compression devices and/or ted hoses.

Intraoperative imaging is used prior to making the incision and throughout the procedure to confirm the adequate level. It is also used to guide instrumentation placement if a fusion procedure is contemplated. Care must be taken when reviewing the scans and other imaging studies to look for aberrations such as a lumbarized sacrum, bifid spinous process or other anomalies.

Adequate laboratory studies should be sent preoperatively including a CBC (to rule out anemia, thrombocytopenia or elevated white blood cell count), electrolytes, coagulation profile and type and screen. Patients with a significant medical history should undergo clearance by an internal medicine specialist and preoperative optimization (eg, beta blockade in hypertensive patients, glucose level monitoring in diabetic patients).

The most common form of facetectomy procedure is discussed here, namely the medial facetectomy, performed for degenerative disc disease, which may be performed in combination with a lumbar laminotomy or laminectomy as well as foraminotomy.

Images depicting facetectomy can be seen below.

Opening and dissection

Extended midline approach

This approach is typically chosen when the pathology extends toward the midline or if signs of stenosis of the central canal exist, such as a large central disc herniation extending toward the foramen or severe degenerative changes involving facet and ligament hypertrophy.

After prepping and draping the patient in the usual sterile fashion, a needle marker is placed in the midline at the level of interest and a lateral lumbar radiograph is obtained in order to verify the adequate level.

A midline skin incision is then performed using a #10 blade and a dissection is carefully carried down through subcutaneous tissue down to the paraspinal fascia using cautery. The Cobb elevator is used to elevate the fascia on both sides, and a self-retaining retractor such as a Weitlaner retractor is then placed in order to expose the fascia.

Using the Bovie cautery the fascia is then incised in the midline down to the spinous processes of one level above and one level below the level of interest. The Cobb elevator with gauze protecting the muscle is used to dissect the paraspinal muscles that are attached to the spinous process and lamina and the dissection is extended laterally to the facet joint. If necessary the bleeding is stopped by a bipolar or a Bovie cautery. This may be done unilaterally or bilaterally, depending on the pathology.

Once the facet joint is exposed, a deeper retractor such as an Oberhill or Adson-Backmann retractor or, alternatively, a self-retaining retractor such as the Versa-Trac, are used to retract the paraspinal muscles and to expose the structures of interest. At this point, a lateral lumbar radiograph is again obtained after placing a marker at the level of the lamina of interest, usually a number 4 Penfield dissector to verify the adequate level.

Alternatively, when addressing a unilateral single level pathology (a lateral recess herniated disc), this approach may be performed as a minimally invasive and/or endoscopic procedure using a tubular retractor system to expose a single lamina and a facet joint level unilaterally.[15]

Far lateral approach

The far lateral approach is typically used for paramedian pathologies that are centered around the facet joint or within the foramen such as a far lateral disc herniation. Often times, this approach is used for a minimally invasive procedure using tubular retractor systems.[17]

After prepping and draping a patient in a usual sterile fashion, a needle marker is placed in the midline at the level of interest and a lateral lumbar radiograph is obtained in order to verify the adequate level.

A paramedian incision is then performed at the level of interest about 2–3 cm from the midline. The incision is extended to about 2.5 cm if the tubular retractor[15] is used or 5 cm if the procedure is done in open fashion by using the Meyerding or Taylor retractor.[18]

In a similar fashion as the extended midline approach, the incision is carried down. The fascia is opened with a Bovie cautery and the underlying paraspinal muscles are identified. Finger dissection is then carried down through the plane between the longissimus and multifidus muscles; this plane is developed down to the facet joint extending down to the dorsal ramus of the involved nerve root.

If the tubular retractor is used, tubes of increasing diameters are then inserted sequentially through the incision, and a tract is developed down to the facet joint. The outer tubular retractor is then inserted over the last tube and attached to the anchoring arm that is attached to the side of the table. Again the adequate level of dissection is verified using a lateral radiograph. Typically, a thin layer of muscle will overlay the facet; this needs to be dissected and resected using the Bovie cautery with an extended sleeve as well as pituitary rongeurs to expose the bony elements of the facet joint. The lateral aspect of the laminas and a pars intra-articularis are exposed.[19]

Bony resection and neural element decompression

Next, a curved curette is used to identify the plane between the 2 laminas and to dissect any remaining soft tissue. The high-speed drill is used to drill the lateral aspect of the lamina and the medial portion of pars interarticularis as well as the medial aspect of the facet joint down to a thin eggshell rim. Drilling starts at the level of the rostral laminae initially because the caudal laminae and facet joint are typically deep to the rostral structures. Frequent irrigation is used during drilling to prevent thermal injury.[13]

Kerrison rongeurs are then used for resection of a thin eggshell portion of the lamina and the medial facet at a rostral level exposing the underlying caudal medial facet joint and inferior lamina. Note that while using Kerrison rongeur, the footplate of the Kerrison must be easily slid with minimal resistance below the bony element to be removed, as any resistance encountered may be secondary to adhesions and may place the patient at higher risk of a dural tear.

The ligamentum flavum (yellow ligament) is then exposed and, again, using a combination of straight and curved curettes, the ligament is dissected from its attachment to the underlying lamina. A ligament typically attaches to the superior medial portion of the lamina and usually a bony resection is extended to the level of the ligament attachment. It is easier to dissect off the ligaments if the bony decompression is extended slightly more rostrally along the superior aspect of the lamina.

The caudal lamina and the medial aspect of the caudal facet are drilled down in a similar fashion using a high-speed drill with a matchstick bur tip. Note a curvature of the caudal facet along its superior aspect. The nerve root is usually impinged right below this curvature. Failure to identify this part may result in a less-than-optimal decompression.  As described above, the Kerrison rongeurs are used to remove the rest of the thin bony rim that is left from drilling.[20]

The pars interarticularis must be identified. The medial portion of the pars may be resected; however, 1 cm of pars should be preserved in order to preserve stability, unless a fusion procedure is contemplated.[12, 10, 15]

Once bony decompression is completed, the yellow ligament can be removed. The ligament is typically preserved until a maximal bony decompression is achieved to protect the underlying neural elements. Using a right-angle blunt hook, a small plane is created between the fibers of the ligaments and, subsequently, using larger, 4-mm Kerrison rongeurs, the ligament is resected. Extremely important is avoiding of pulling on the ligament when resecting it; instead, it should be removed piecemeal with rongeurs without causing any tension on the underlying dura. This procedure exposes the underlying thecal sac. Next, using a Woodson instrument, the neural foramen is identified between 2 pedicles of the vertebrae above and below. Kerrison rongeurs are then used to underbite the remaining lateral aspect facet joints and decompress the neural foramen and the nerve root. The adequacy of decompression is verified again by passing Woodson instrument, which should pass with no resistance through that foramen. In a similar fashion, the neural foramen of the level below is also identified distal to the caudal pedicle, and a foraminotomy can be performed at that level if indicated.

When addressing herniated disc pathology, the thecal sac is then retracted medially using a nerve root retractor and the underlying herniated or bulging disc is exposed. A small needle marker is placed in the disc to verify exact location and a lateral lumbar radiograph is obtained before an annulotomy. This typically exposes also epidural veins and some epidural bleeding follows at that site. The bipolar cautery at a low setting is used to stop any bleeding. The use of Gelfoam powder with thrombin or FloSeal is also recommended for hemostasis before starting a discectomy.

The discectomy is then carried in the usual fashion. When dealing with cases of disc extrusion, the disc extruded fragment should be immediately visualized once retracting the thecal sac and may be then resected using pituitary rongeurs. In cases of contained disc herniations, an annulotomy is performed using a #15 blade, and the cuts through the annulus fibrosis are typically performed parallel to the thecal sac to avoid a thecal sac injury.

Subsequently, pituitary rongeurs are used to remove the bulging portion of the disc. The remainder of the disc may be also resected in a piecemeal fashion using straight curettes to dissect the rest of the nucleus pulposus from the interbody space and using reverse angled (Epstein’s) as well as angled curettes to remove the disc portions that are more medial and lateral. Subsequently, pituitary rongeurs that are straight, up-angled, and down-angled are used to resect as much disc as possible from within the disc space. Finally, the curettes are used to verify that no free fragments of nucleus pulposus (which may herniate at a later time) remain within the disc space. Space is then irrigated with antibiotic saline solution. This is done by using a small red rubber catheter to prevent future discitis or infection.[21]

In cases in which a lumbar fusion is contemplated, such as in cases of primarily axial back pain or a significant axial back pain in combination with radicular symptoms, the facet joint may be resected entirely with all resected bone fragments being preserved and cut down to smaller pieces for a later use as locally harvested bone graft. The details of lumbar fusion and instrumentation are beyond the scope of this article.[22]

Closure

Before a closure, an adequate hemostasis should be achieved after a profuse irrigation with an antibiotic saline solution. Hemostasis is achieved in the usual fashion using the bipolar cautery. The bipolar cautery should be set at a low setting when close to the thecal sac or neural elements to avoid any thermal injury to the surrounding nerves. Gelfoam powder with thrombin or FloSeal is then used if necessary to control any remaining venous oozing. Irrigation is then performed again.

A wound closure is done in layers starting with the paraspinal muscles and fascia, which are closed using 0-Vicryl interrupted sutures. The subcutaneous tissues are closed using 2-0 or 3-0 Vicryl interrupted buried sutures. The skin may be closed with staples or subcuticular 3-0 Monocryl suture. A Blake or Jackson-Pratt drain may be left in place along the bony elements and tunneled subcutaneously to a distal exiting site if any oozing of blood during closure is observed.

Adequate dressings are applied and the patient is then turned back to the supine position and extubated.

New concepts

A disc replacement with a preservation of motion has been used to address lower back pain of discogenic origin. Facet replacement has been used lately to address instability created by the surgical decompression or to address chronic instability or replace painful facet joints.[2]

Postoperative considerations are as follows:

• A patient is mobilized 6 hours after the procedure.

• Adequate analgesia is given, such as patient controlled analgesia (PCA pump) or intravenous narcotics. Typically, patients who are on chronic pain medications are restarted on their preoperative medications and may have added breakthrough intravenous analgesics.

• The patient may be kept on antibiotics for 24 hrs.

• If stable and ambulatory, the patient may be discharged in 24 hrs.

Complications

Complications may include the following:

• Extensive manipulation of the nerve root should be avoided, as it may cause persistent pain postoperatively.

• Dural tears should be treated under the microscope. The tear should be exposed in its entirety by removing more bone. It is then sutured with 5-0 Prolene. Fibrin glue is then placed along the dural surface.

• Wound infection is prevented with antibiotic prophylaxis. Postoperatively, the wound is kept clean and the dressing changed every day.

• Spinal instability can be caused by excessive drilling and removal or wider portions of the facet or the pars interarticularis.

• CSF leakage from the wound can be treated with wound reinforcement and lumbar drain placement.

• Epidural or subcutaneous hematoma may need reoperation.

• Disc re-herniation or herniation of residual fragment may need reoperation.

• Injury to the thecal sac or cauda equina can occur.

• Neuropathic or complex regional pain syndrome may be a source of persistent pain.

• Positioning injuries should be prevented (eg, brachial plexus, ulnar nerve injuries).

• After multilevel procedures for removal of tumors, long-term instability or deformity may occur.[23]

Long-term monitoring

See the list below:

• Return to work status is evaluated after 1–2 months.

• The patient is followed monthly for at least 3 months postoperatively via monthly visits.

• An LSO corset can be given to the patient to wear during the recovery on an intermittent basis.

• In cases of lumbar fusion, serial radiographs are obtained monthly to assess the adequacy of the instrumentation in bony bridge formation.[24, 15]

• In cases of workers compensation, maximal medical improvement can be evaluated after 3 months and may require the performance of a functional capacity evaluation by a trained physical therapist prior to returning to work

Patient Education

Patients are instructed not to lift any heavy objects with the typical weight restriction of about 10–20 pounds.[25, 26]

Patients are also instructed to avoid sitting or standing for prolonged period of time greater than 20 minutes and also avoid riding in a motorized vehicle for more than 20 minutes at a time without frequent breaks in which the patient will get out of the vehicle and stretch.

During the healing process, typically, some axial muscular back pain exists; however, the radicular symptoms should improve. Improvement may be seen immediately postoperatively or may take several days to weeks to occur, especially in cases in which some neuropathic-type damage or chronic changes within the nerve root or dorsal root ganglion occurred.

Patients should also be instructed that, given the fact that they have undergone a decompression, they will have some limitations for the rest of their lives with regards to any type of strenuous activity. They should be very careful with their use of their lower back. Patients should be referred to a physical therapist, occupational therapist are other allied health or posture specialists (such as an Alexander technique specialist[27] ) to assist them with training for adequate use of their lower back.

As a general rule, in all cases of degenerative spine disease, the patient should be instructed to stop smoking if a smoker or lose weight if overweight.